The overall goal of our research is to determine how specific cellular properties of neurons act to control various features of behavior. We will focus on the neural control of the cardiovascular system in the marine mollusc Aplysia californica. A three level approach to this problem will be used: (1) At the behavioral level, we will examine the cardiovascular indicators of a change in motivational state -- the arousal state elicited by food stimuli. (2) We will extend the analysis of the neural circuits controlling the cardiovascular system, focussing particular attention on the input it receives from the network that controls feeding. (3) We will examine the cellular electrophysiological properties of neurons in the cardiovascular control circuit to determine how these properties influence various aspects of behavior. With regard to cellular properties of neurons, we will ask four experimental questions: (1) How are the different repetitive firing characteristics of various neurons related to their specific roles in the generation of behavior? (2) What functions do the different species of voltage-sensitive conductance channels serve in the control of repetitive firing and other aspects of cellular function, such as axonal transport? (3) What factors account for the differences between different identified cells in the properties of a given type of conductance channel? (4) To what extent do the repetitive firing characteristics of a particular identified cell exhibit short term changes (with arousal) or long term changes (with age)?